CMUT Array Segmentation via Dual-Step Cutting
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Solution Overview
Problem
Current methods for packaging and interconnecting capacitive micromachined ultrasonic transducer (cMUT) arrays, especially for 1-D arrays, are complex and not cost-efficient, often requiring complex drilling or cutting techniques that result in performance limitations and are not suitable for flexible arrays, with a trade-off between parasitic capacitance and conductivity.
Innovation Solution
A method involving two cutting steps to electrically separate transducer elements from each other, forming patterned openings in the substrate to create partially separated segments that can be individually addressed as bottom electrodes, allowing for stable separation and potential removal from the substrate, particularly suitable for 1-D arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If drilling holes and filling with conductive material is used to make bottom electrodes individually addressed, then interconnection is achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The substrate is segmented into multiple isolated regions using trenches, with each region containing a transducer element and its associated bottom electrode. This segmentation allows each bottom electrode to be individually addressed without requiring complex drilling and filling operations, as the isolation is achieved through the trench structure during standard fabrication processes.
Solution Approach 2:
The trenches for isolating substrate regions are formed during the fabrication process before final assembly and packaging. This preliminary action eliminates the need for subsequent drilling and conductive material filling operations, simplifying the overall manufacturing process and reducing device complexity.
2Reliability
If drilling and filling method is used for interconnection, then electrical connection is achieved, but parasitic capacitance increases and conductivity decreases
Solution Approach 1:
The trench-based isolation structure creates well-defined electrical boundaries between adjacent transducer elements. This segmentation provides controlled impedance paths and minimizes parasitic capacitance between elements, while the conductive material filling the trenches ensures low-resistance electrical connections to the bottom electrodes, thereby improving overall connection quality without the harmful trade-offs of the drilling-filling method.
3Ease of manufacture
If complex drilling or cutting techniques are used, then interconnection is achieved, but manufacturing cost increases and flexibility is reduced
Solution Approach 1:
The trench isolation structure can be easily configured in different patterns (linear arrays, phased arrays, etc.) by simply changing the trench layout during fabrication. This segmentation approach provides manufacturing flexibility and adaptability for various array configurations without requiring complex drilling or cutting techniques, enabling cost-effective production of different transducer array designs.
4Ease of manufacture
If top moving electrode is used as individually addressed electrode, then ease of fabrication is improved, but performance and packaging considerations are compromised
Solution Approach 1:
Instead of addressing the top moving electrode as is conventional, this invention inverts the approach by making the bottom fixed electrode the individually addressed electrode through trench isolation. This inversion enables better performance and packaging suitability while maintaining fabrication simplicity through the standardized trench formation process integrated into the manufacturing flow.
Data Source
AI summary
A method for fabricating electrostatic transducers and arrays electrically separates the substrate segments of the transducer elements from each other using a technique involving two cutting steps, in which the first step forms a patterned opening in the substrate to make a partial separation of substrate segments, and the second step completes the separation after the substrate segments have been secured to prevent instability of the substrate segments upon completion of the second step. The securing of the substrate segments may be accomplished by filling a nonconductive material in the partial separation or securing the transducer array on a support substrate. When the substrate is conductive, the separated substrate segments serve as separate bottom electrodes that can be individually addressed. The method is especially useful for fabricating ID transducer arrays.